Abstract Emergency responders, including paramedics, fire fighters, and police, routinely come into contact with individuals who have overdosed and play a critical role in administering naloxone to reverse opioid-related overdose. However, mechanisms to link these individuals to medication-assisted treatment (MAT) following an overdose are lacking. This study targets individuals in Chicago who have received naloxone administered by first responders within the past week to reverse an overdose, but who have not entered into MAT. Study participants will be recruited through partnerships with the Chicago Fire Department (CFD) and Police Department (CPD); first responders will be trained to seek consent from individuals who are alert and oriented after receiving naloxone for future contacts by research staff as part of the naloxone standard protocol. Those who consent will be contacted and screened for study eligibility within one week of naloxone administration; eligible participants will be randomly assigned either to the control group, i.e., referral to MAT as usual, or to Recovery Initiation and Management after Overdose (RIMO), an assertive linkage and recovery support intervention. This intervention builds on an evidenced-based intervention for treatment linkage, monitoring, and recovery support evaluated in 3 prior clinical trials by the study team. The Phase 1 (R21) Pilot Aim is to: Adapt and pilot test an assertive intervention (RIMO) to link individuals with opioid use disorders (OUD) whose overdose has been reversed by naloxone administered by first responders to MAT. Forty individuals will be recruited from two communities in Chicago with high rates of opioid-related overdose and naloxone administrations and will be randomly assigned to receive either the ?referral only? control or ?RIMO?. Assessments will be completed at baseline and outcomes collected from treatment records. Recruitment referral methods and RIMO will be refined based on pilot study findings, focus groups with RIMO participants, and input from study partners and advisory board, and the existing intervention procedures manual will be adapted. The Phase 2 (R33) Experiment will use the study recruitment and RIMO procedures refined in Phase 1 to recruit a total of 400 individuals and randomly assign them either to the referral only control or RIMO. All participants will receive standardized assessments at baseline and 1, 3, 6, 9, and 12 months post-randomization. Phase 2 Study Aims are to evaluate RIMO?s: 1. direct effect on linkage to MAT, length of time on medication, dropout, and total days of MAT 2. direct and indirect (via MAT) effects on time to relapse, opioid use, and opioid-related overdose 3. direct and indirect (via MAT and opioid use) effects on opioid-related fatalities, OUD symptoms, physical health, mental health and the cost of health care utilization.